DQW Cryogenic Magnetic Shield Internal Review Niklas Templeton 06/05/15

Contents Specification Opera Magnetic Analysis Overview –Design Approach –Common Features Design & Assembly Procedure –DQW –RFD Shield Analysis –Thermal Stress –Self Weight XYZ 1

Specification Less than 1µT on cavity surface Cold Magnetic Shield –1mm APERM Cryophy (to be used with 3mm Mu Metal outer shield) –Internal to Helium Vessel –Suspended in 2K Helium –Mounted off Helium vessel – no cavity connection Designed for (worst case) earth magnetic field. Local sources to be isolated separately –Earths South to North Field 48µT –SPS ambient Magnetic field with moderately shielded Busbars <200µT Magnetic shielding for SPL cavities: T Junginger 2010 Estimate of the Ambient Magnetic Field in the SPS Crab Cavity Location: J Bauche, A Macpherson

Summary of Opera Analysis - Kiril Maranov The magnet group within ASTeC (STFC) have converted the mechanical design CAD files into a simplified geometry acceptable for Opera 3D (Tosca) and then assessed shielding performance based on simulations. Two shielding solutions were considered: a single-layer solution (mu- metal only) and a double-layer solution (mu-metal + cryoperm) The conclusion from this work is to go ahead with the double-layer solution. The single layer solution meets the spec by a narrow margin, but there is no room for contingency and the risk is higher. 3

Magnetic shielding effect is anisotropic The external field is radial The external field is axial  A cylinder is twice as effective against radial field as against axial field. 4

Single layer: the field is parallel to the long side B Earth =60µT A single-layer shield is within spec (~0.5 µT) at the cavity locations, but this gives a limited factor of safety. B>1 µT 5

Performance: the field is parallel to the long side B Earth =60µT B>1 µT B<< 0.1 µT (very small!) 6

Shield Design Approach Satisfy space constraints –Internal to Bolted Helium Vessel –Close fitting to cavity Feasible assembly 1.Minimise number & size of penetrations 2.Ease of manufacture & assembly –Minimise number of panels –Bent / Folded sheet –*Pressed / Formed panels possible future batch shield orders 3.Maximise penetration attenuation 4.Maximise curvature 7

Reason for Close fitting shield High field regions requiring <1µT Reference - F. Pobell, Matter and Methods at Low Temperatures. Springer-Verlag, third ed.,

Common Design Features Helium Holes Shield peppered with at least 142 x Ø3mm holes on mm pitch for helium transfer 142 holes give 10cm 2 transfer area, so that at worst case heat load (10W) heat flow is at least 1W/cm 2 1mm APERAM Cryophy - Cold Rolled Strip Panels to be manufactured from Cryophy sheet metal which is cut, bent/folded, and fastened using self clinching nuts & spring washers 9

Common Design Features Tubular Shielding Prevents field penetration through openings. Ideally H = ØD Fitted & Curved Shape More effective at containing channelled magnetic flux Additional Cover Strips Overlapping joints prevent gaps & allows magnetic flux to follow a continuous low- reluctance path Flexi-Mounts Flexible Gr2 Titanium mounts connect the shield to the Helium Vessel. 8 mounting pairs are utilized in 3 orientations for maximum shield stability 10

YZX DQW Shield Design & Assembly Concept AConcept BConcept C No. of panels997 Curvature YZR40, R10, R50, R50 -R50, R50 Curvature XY-R100, R40, R30, R100 R100, R40 A B C Concept Analysis 11

DQW Shield Design & Assembly Assembled Shield Mass: ~10kg 12

DQW Shield Design & Assembly YZX 13

DQW Shield Design & Assembly YZX 2 Bottom Panels assembled 1 st Cavity orientation shown upside down for clarity 14

DQW Shield Design & AssemblyYZ X Shield & cavity mounted to base plate of the Helium Vessel Top End caps are attached as well as bottom side panel and Dummy beam pipe attenuation sleeve. 15

DQW Shield Design & Assembly Final 2 top panels are brought into place and remaining cover strips and brackets are fastened 16

DQW Shield Design & Assembly Side and top Vessel walls are assembled with remaining Flexi-Mounts before Helium Vessel is closed 17

RFD Shield Design & Assembly RFD Helium Vessel 20/04/15 Assembled Shield Mass: ~10kg 18

RFD Shield Design & Assembly 19

RFD Shield Design & Assembly Pre-assembled shield body is assembled Top and Bottom 20

RFD Shield Design & Assembly Shield Body is mounted to Helium Vessel Base 21

RFD Shield Design & Assembly Split folded-end panels are assembled around 3 ports End Cover is assembled to main body and fastened with cover panels and brackets 22

RFD Shield Design & Assembly 2 Curved-End panels are assembled around Beam Pipe 23

RFD Shield Design & Assembly Split panels complete the Shield at the FPC & HOM Ports Remaining cover strips are assembled 24

RFD Shield Design & Assembly Flexi Mounts are connected and Helium Vessel is assembled 25

FEA: Cool Down & Self Weight Material Data Helium Vessel & Flexi-Mounts: Titanium Grade2 (ES371110) –RT Yield Strength= 275MPa –Thermal Expansion from RT to -269K = -5.2 E-6.K Magnetic Shield: Aperam Cryophy (Magnetic Shielding LTD) –RT Yield Strength = 280MPa –Thermal Expansion from RT to -269K = -8 E-6.K 26

DQW & RFD Thermal Stress Loads & Constraints Cool down from RT to 2K Fixed at input coupler interface Results Solution contains erroneous result due to skew mesh geometry Stress > 150Mpa shown in red Some localised high stresses at shield connections Conclusion Cryophy Stresses affects shielding properties in immediate stress location, localised stresses are (at worst) comparable to a small hole – effect is negligible. Localised stress can be avoided using sufficient clearance at connections. 27

DQW Self Weight Horizontal Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS Z direction Max shield deformation 0.08mm Max shield stress 13MPa 28

DQW Self Weight Vertical Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS Y direction Max shield deformation 0.04mm Max shield stress 14MPa 29

DQW Self Weight Side Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS X direction Max shield deformation 0.07mm Max shield stress 32MPa 30

DQW Self Weight Horizontal Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS Z direction Max shield deformation 0.01mm Max shield stress 9MPa 31

RFD Self Weight Vertical Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS Y direction Max shield deformation 0.01mm Max shield stress 9MPa 32

RFD Self Weight Side Fixed at Flexi Mount – Helium Vessel interface Gravity applied in ANSYS X direction Max shield deformation 0.02mm Max shield stress 27MPa 33

Discussions with Magnetic Shielding LTD We have liaised with Magnetic Shields LTD from the UK throughout the design of the shield. We obtained a budget cost for the previous shield concepts (welded helium vessel). Cost estimate was £8-12K (excluding VAT) per shield New designs could be more expensive, up to ~£15K (€20K) Formed / pressed shield panels are feasible for larger quantity orders. 34

Thank You! Questions?